Data Structures and Algorithms in Java[1].pdf - Fulvio Frisone

a text editor class may wish to define a related cursor class. Defining the cursor
class as a nested class inside the definition of the text editor class keeps these two
highly related classes together in the same file. Moreover, it also allows each of
them to access nonpublic methods of the other. One technical point regarding
nested classes is that the nested class should be declared as static. This
declaration implies that the nested class is associated with the outer class, not an
instance of the outer class, that is, a specific object.
Packages
A set of classes, all defined in a common subdirectory, can be a Java package.
Every file in a package starts with the line:
package package_name;
The subdirectory containing the package must be named the same as the package.
We can also define a package in a single file that contains several class definitions,
but when it is compiled, all the classes will be compiled into separate files in the
same subdirectory.
In Java, we can use classes that are defined in other packages by prefixing class
names with dots (that is, using the '.' character) that correspond to the other
packages' directory structures.
public boolean Temperature(TA.Measures.Thermometer
thermometer,
//…
}
int temperature) {
The function Temperature takes a class Thermometer as a parameter.
Thermometer is defined in the TA package in a subpackage called Measures.
The dots in TA.Measures.Thermometer correspond directly to the directory
structure in the TA package.
All the extra typing needed to refer to a class outside of the current package can get
tiring. In Java, we can use the import keyword to include external classes or
entire packages in the current file. To import an individual class from a specific
package, we type the following at the beginning of the file:
import packageName.classNames;
For example, we could type
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